PERSPECTIVES ON THE CONTROL OF HEPATITIS-A BY VACCINATION

The availability of an inactivated hepatitis A virus (HAV) vaccine, and the development of live attenuated virus vaccines against hepatitis represent great advances in the effort to control an important cause of viral hepatitis. There are a number of ways hepatitis A vaccines could be used, depending on the epidemiology of HAV infection in the country concerned, the cost of the product, the duration of protection that the vaccine affords and its effectiveness for postexposure prophylaxis. Expert groups could recommend vaccine to individuals who are at higher risk of exposure to hepatitis A as a result of behaviour, lifestyle or occupation, or to all infants and/or adolescents. The major public health problem with hepatitis A occurs in developing countries and regions with 'transitional economies' such as Eastern Europe and certain Middle Eastern countries. These countries have high levels of viral circulation, large cohorts of susceptible older children and adults, and high rates of HAV morbidity. Given the experience with hepatitis B vaccine and the economic and political realities of global immunization policy, it is unlikely that the Expanded Programme on Immunization and traditional vaccine donors will take a great interest in HAV vaccine in the near future. Individual countries may, however, decide to use hepatitis A vaccine on a widespread basis. Model cost effectiveness studies are needed.for both developing and developed countries to help decide the feasibility of such widespread use. WHO has been involved in activities relevant to hepatitis A vaccine for many years. The Programme.for Vaccine Development, through its Steering Committee on Hepatitis and Polio, has funded more than 25 research projects on HAV since 1984. These projects have included studies of the antigenic sites responsible for immunity, the molecular and genetic basis of viral attenuation, growth in tissue culture, the immunogenicity of subunit antigens, hepatitis A-poliovirus chimeras, production of monoclonal antibodies, the molecular epidemiology of HAV and the preparation of live attenuated HAV vaccines. The Programme for Control of Viral Hepatitis is planning a meeting to prepare guidelines for use of hepatitis A vaccines in developed and developing countries. The Biologicals Programme at WHO is also planning a meeting on requirements.for the preparation of inactivated hepatitis A vaccine and guidelines for the further development and use of live attenuated vaccines.